U.S. patent number 6,930,399 [Application Number 10/343,519] was granted by the patent office on 2005-08-16 for high reliability non-conductive adhesives for non-solder flip chip bondings and flip chip bonding method using the same.
This patent grant is currently assigned to Korea Advanced Institute of Science and Technology, Telephus Inc.. Invention is credited to Kyung-Wook Paik, Myung-Jin Yim.
United States Patent |
6,930,399 |
Paik , et al. |
August 16, 2005 |
**Please see images for:
( Certificate of Correction ) ** |
High reliability non-conductive adhesives for non-solder flip chip
bondings and flip chip bonding method using the same
Abstract
The method of the present invention comprises the steps of:
providing an IC chip having I/O pads, each having a non-solder bump
such as Au or Cu stud bump or Ni.backslash.Cu.backslash.Au bump
formed thereon, and a substrate having metal electrodes formed
thereon; applying a film-type non-conductive adhesive (NCA) to the
chip or substrate, the adhesive including solid-phase bisphenol A
type epoxy resin, liquid-phase bisphenol F type epoxy resin,
solid-phase phenoxy resin, methylethylketone/toluene solvent,
liquid-phase hardener, and non-conductive particles; and
thermo-compressing the IC chip to the substrate so that the
non-solder bump and the metal electrode can be mechanically and
electrically connected. The NCA of the present invention has high
reliability since it has lower thermal expansion coefficient and
dielectric constant than conventional NCAs and has excellent
mechanical and electrical characteristics. In addition, the NCA can
be effectively selected at need and applied to diverse processes
since it can be made to a form of paste rather than film. The
method of the present invention is harmless to the environment
since it does not employ conventional solder bumps using solder as
a chief ingredient.
Inventors: |
Paik; Kyung-Wook (Taejon,
KR), Yim; Myung-Jin (Taejon, KR) |
Assignee: |
Korea Advanced Institute of Science
and Technology (KR)
Telephus Inc. (KR)
|
Family
ID: |
36686694 |
Appl.
No.: |
10/343,519 |
Filed: |
January 30, 2003 |
PCT
Filed: |
August 02, 2001 |
PCT No.: |
PCT/KR01/01313 |
371(c)(1),(2),(4) Date: |
January 30, 2003 |
PCT
Pub. No.: |
WO02/15259 |
PCT
Pub. Date: |
February 21, 2002 |
Foreign Application Priority Data
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|
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Aug 2, 2000 [KR] |
|
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2000-44829 |
|
Current U.S.
Class: |
257/783; 257/778;
257/E21.514 |
Current CPC
Class: |
C08L
63/00 (20130101); C09J 171/00 (20130101); H01L
24/11 (20130101); H01L 24/83 (20130101); C09J
11/04 (20130101); H01L 24/29 (20130101); C08G
59/226 (20130101); C09J 7/10 (20180101); C08L
63/00 (20130101); C08L 71/00 (20130101); C09J
171/00 (20130101); C08L 63/00 (20130101); H01L
2224/13647 (20130101); H01L 2924/0103 (20130101); H01L
2224/05573 (20130101); H01L 2924/01058 (20130101); H01L
2924/01005 (20130101); H01L 2924/01013 (20130101); H01L
2924/14 (20130101); H01L 2224/05026 (20130101); H01L
2924/01043 (20130101); H01L 2924/0665 (20130101); H01L
2224/13155 (20130101); H01L 2224/0558 (20130101); H01L
2224/73204 (20130101); H01L 2924/0132 (20130101); H01L
2224/05001 (20130101); H01L 2924/01079 (20130101); H01L
2924/07802 (20130101); H01L 2924/01006 (20130101); H01L
2924/07811 (20130101); H01L 2924/01047 (20130101); H01L
2224/838 (20130101); H01L 2224/83192 (20130101); H01L
2224/13644 (20130101); H01L 2924/00013 (20130101); H01L
2924/01029 (20130101); C09J 2463/00 (20130101); H01L
2924/01033 (20130101); H01L 2924/014 (20130101); C08G
2650/56 (20130101); H01L 2224/16225 (20130101); H01L
2224/1134 (20130101); H01L 2224/2919 (20130101); C09J
2461/00 (20130101); H01L 2924/01082 (20130101); H01L
2924/01087 (20130101); H01L 2924/0781 (20130101); H01L
2224/13155 (20130101); H01L 2924/00014 (20130101); H01L
2224/13644 (20130101); H01L 2924/00014 (20130101); H01L
2224/13647 (20130101); H01L 2924/00014 (20130101); H01L
2924/00013 (20130101); H01L 2224/13099 (20130101); H01L
2224/2919 (20130101); H01L 2924/0665 (20130101); H01L
2924/00 (20130101); H01L 2924/0665 (20130101); H01L
2924/00 (20130101); H01L 2924/0132 (20130101); H01L
2924/01006 (20130101); H01L 2924/01014 (20130101); H01L
2224/16225 (20130101); H01L 2224/13155 (20130101); H01L
2924/00 (20130101); H01L 2924/07811 (20130101); H01L
2924/00 (20130101); H01L 2924/07802 (20130101); H01L
2924/00 (20130101); H01L 2224/05124 (20130101); H01L
2924/00014 (20130101); C09J 2463/00 (20130101); C09J
2461/00 (20130101) |
Current International
Class: |
C08L
63/00 (20060101); C08G 59/00 (20060101); C08G
59/22 (20060101); C09J 11/02 (20060101); C09J
11/04 (20060101); C09J 7/00 (20060101); C09J
171/00 (20060101); H01L 21/60 (20060101); H01L
21/02 (20060101); H01L 023/48 () |
Field of
Search: |
;257/783,778 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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1997-0061017 |
|
Aug 1997 |
|
KR |
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1020000046722 |
|
Jul 2000 |
|
KR |
|
Other References
English language abstract of Korean Patent Publication No.
1020000046722. .
English language abstract of Korean Patent Publication No.
1997-0061017..
|
Primary Examiner: Nelms; David
Assistant Examiner: Hoang; Quoc
Attorney, Agent or Firm: Marger Johnson & McCollom,
P.C.
Claims
What is claimed is:
1. Non-conductive adhesive for flip chip bonding that is dried and
has the form of a film, comprising: 6.about.10 wt % of solid-phase
bisphenol A type epoxy resin; 15.about.25 wt % of liquid-phase
bisphenol F type epoxy resin; 12.about.18 wt % of solid-phase
phenoxy resin; 32.about.40 wt % of solvent mixture with
methylethylketone and toluene with the ratio of 1:3 in vol %;
8.about.14 wt % of liquid-phase imidazole hardener; and 6.about.20
wt % of non-conductive SiO2 or SiC particles.
2. Non-conductive adhesive for flip chip bonding of claim 1,
wherein the thickness of the film is 10.about.50 .mu.m.
3. Non-conductive adhesive for flip chip bonding of claim 1,
wherein an epoxy adhesion enhanced layer with the thickness of
2.about.5 .mu.m, the epoxy adhesion enhanced layer being made by
mixing 6.about.10 wt % of solid-phase bisphenol A type epoxy resin,
15.about.25 wt % of liquid-phase bisphenol F type epoxy resin,
12.about.18 wt % of solid-phase phenoxy resin, 32.about.40 wt % of
solvent mixture with methylethylketone and toluene with the ration
of 1:3 in vol %, and 8.about.14 wt % of liquid-phase imidazole
hardener are contained and drying it.
4. Non-conductive adhesive for flip chip bonding of claim 1,
wherein the non-conductive SiO.sub.2 or SiC particles have a size
of 0.1.about.1 .mu.m.
5. Non-conductive adhesive for flip chip bonding of claim 1,
wherein the hardener is 15.about.30 wt % to epoxy resin and the
non-conductive particle is 10.about.30 wt % to the whole
non-conductive adhesive.
6. Non-conductive adhesive for flip chip bonding that has the form
of a paste, comprising: 40.about.75 wt % of liquid-phase bisphenol
A or F type epoxy resin; 15.about.30 wt % of liquid-phase imidazole
type hardener; and 10.about.30 wt % of non-conductive SiO2 or SiC
particles.
7. Non-conductive adhesive for flip chip bonding of claim 6,
wherein the non-conductive SiO2 or SiC particles have a size of
0.1.about.1 .mu.m.
Description
TECHNICAL FIELD
The present invention relates to a non-conductive adhesive
(hereinafter referred to NCA) and a method for flip chip bonding
using the same. Especially the present invention relates to a
non-conductive adhesive with smaller coefficient of thermal
expansion and dielectric constant and superior mechanical and
electrical features compared to conventional NCA and a method for
flip chip bonding using the same.
BACKGROUND ART
The electronic packaging technology is a comprehensive and diverse
system manufacturing technology including all steps from a
semiconductor device to a final finished product. Recently, the
technologies in semiconductor are developing into integration of
more than million cells, and large number of I/O pins, large size
die, dissipation of large amount of heat and high electrical
performance in case of a non-memory device. However, the electronic
packaging technology for such devices has not followed the rapid
development of semiconductor industry.
The electronic packaging technology is an important technology that
affects performance, size, price and reliability of final
electronic products. The importance of this technology is being
emphasized according to the development of electronic products
pursuing high electric performance, ultra small size/high density,
low power, multi-function, high speed signal processing and
permanent reliability.
In line on the trend, the flip chip bonding technology, one of the
technologies that connect a chip to a substrate electrically has
drawn a lot of attention. However, the flip chip bonding technology
involves complex bonding processes utilizing a existing solder
comprising coating of solder flux on a substrate, aligning a chip
which is formed of a solder bump and a substrate which is formed of
a surface electrode, reflowing of a solder bump, removing of
remained flux, filling of underfill and hardening. So this
technology increases the price of final products.
Therefore, in order to simplify the aforementioned complex process,
a packaging technology in a wafer state which coats and processes
polymeric material with flux and underfill functions in a wafer
state draws attention. In addition a study on a flip chip bonding
technology using a conductive adhesive is in progress. The
conductive adhesive has advantages of low price compared to a
general solder flip chip, possibility of ultrafine electrode pitch,
environmentally friendliness due to not using flux or lead
components, and processibility at low temperature.
The conductive adhesive can be divided into an anisotropic
conductive adhesive (hereinafter referred to ACA) and an isotropic
conductive adhesive, and comprises: conductive particles such as
Ni, Au/polymer or Ag; and thermosetting, thermoplastic or blend
type insulating resin integrating advantages of them. The research
on flip chip technology utilizing expensive but environmentally
friendly ACA as a connection material has been very active. In
order to support the research the development of ACA material and
application of ACA flip chip technology have been also very
popular.
In addition to the flip chip bonding technology using the
conductive adhesive, the technology using NCA that does not have
conductive particles is introduced. However, there has been a
problem of low reliability for conventional NCA material because it
exhibits a large coefficient of thermal expansion and dielectric
constant and also has inferior mechanical and electrical
features.
As explained above, since it uses solder bump, existing flip chip
packaging technology is not only complicated in its assembly
process, but also not environmentally friendly. And packaging cost
is high due to the cost of ACA material when ACA is used. When NCA
is used, reliability of the product is lowered because of large
coefficient of thermal expansion and dielectric constant and its
inferior mechanical and electrical features. Considering the
reality that electronic packaging technology is on the rise as an
important field in creating added value of products, it is a very
important task to develop environmental friendly flip chip
technology that solves the existing problems and can substitute
existing solder connection.
DISCLOSURE OF THE INVENTION
Therefore, it is the object of this invention to provide NCA for
flip chip bonding that is less expensive than ACA but with smaller
coefficient of thermal expansion and dielectric constant and with
superior mechanical and electrical features and high reliability
compared to conventional NCA.
It is another object of this invention to provide a method for flip
chip bonding that is environmentally friendly and can increase the
reliability of product using the NCA provided by this invention,
using gold or copper stud bump instead of solder bump, and using
non-solder bump such as electroless nickel/copper/gold bump.
One example of non-conductive adhesive used for flip chip bonding
in this invention is in the form of a film comprising solid-phase
bisphenol A type epoxy resin, liquid-phase bisphenol F type epoxy
resin, solid-phase phenoxy resin, methylethylketone/toluene
solvent, a liquid-phase hardener, and non-conductive particles. It
is desirable that the thickness of film is 10.about.50 micrometers
(.mu.m) and an extra layer of epoxy resin on both sides of the film
with the thickness of 2.about.5 .mu.m is added to enhance the
adhesion.
Another example of non-conductive adhesive used for flip chip
bonding in this invention is in the form of a paste comprising
liquid-phase bisphenol A or F type epoxy resin, liquid-phase
hardener, and non-conductive particle.
In the examples of non-conductive adhesive used for flip chip
bonding in this invention, the non-conductive particle has the size
of 0.1.about.1 .mu.m and are comprised of SiO2 or SiC. The hardener
is an imidazole type hardener. Also, the hardener is 15.about.30 wt
% of the epoxy resin and the non-conductive particle is 10.about.30
wt % of the whole non-conductive adhesive.
A method for flip chip bonding according to one example of this
invention comprises steps of: preparing an IC chip that multiple
number of non solder bumps are formed at the I/O stage and a board
that metal electrode is formed on the surface; gluing the non
conductive adhesive according to one example of the present
invention on the substrate; aligning the bump on the metal
electrode; and thermo-compressing the IC chip to the board so that
the bump is plastic deformed and the bump and the metal electrode
are connected mechanically and electrically.
A method for flip chip bonding according to another example of in
this invention comprises steps of: preparing an IC chip that
multiple number of non solder bumps are formed at the I/O stage and
a board that metal electrode is formed on the surface; coating the
non-conductive adhesive according to another example of the present
invention on the substrate; aligning the bump on the metal
electrode; and thermo-compressing the IC chip to the board so that
the bump is plastic deformed and the bump and the metal electrode
are connected mechanically and electrically.
In one or another method for flip chip bonding in this invention,
the step that forms the non-solder bump comprises: forming a metal
pad at the I/O stage of IC chip; and forming a gold or copper stud
bump on the metal pad.
Here, after the stud bump formation step, it is desirable that a
coining process that applies the pressure to the end of stud bump
is added so that the end of stud bump becomes even. Whether coining
process needs to be added or not is decided upon the strength of
the stud bump material and its plastic deformation characteristics.
Normally coining process is not necessary for gold stud bump,
however, is better to be added for copper stud bump.
In one or another method for flip chip bonding in this invention,
the step that forms the non-solder bump comprises: forming a metal
pad at the I/O stage of IC chip; and forming nickel/copper/gold
bump by adding nickel, copper, and gold layer successively to the
metal pad in a electroless method. Copper is less hard than nickel
and is easily plastically deformed, therefore, nickel/copper bump
is electrically connected to metal electrode of the board stably.
In this way, the said copper layer is formed.
Meanwhile, depending on the case, zincate treatment on the metal
pad can be added after the formation of the metal pad.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A to FIG. 1C are schematic drawings to describe the method of
formation of gold stud bump 140 before coining;
FIG. 1D is a sketch to describe the method of formation of gold
stud bump 140a that the end of which becomes even by coining
process;
FIG. 1E is a picture that shows the gold stud bump 140 of FIG. 1C
before coining;
FIG. 1F is a picture that shows the gold stud bump 140a of FIG. 1D
after coining;
FIG. 2A to FIG. 2D are cross-sectional views to describe the method
of formation of electroless nickel/copper/gold bump.
FIG. 2E is a picture to show electroless nickel/copper/gold bump of
FIG. 2D;
FIG. 3 is a sketch to explain the method for flip chip bonding in
this invention; and
FIG. 4A and FIG. 4B are cross-sectional views to present the
results of flip chip bonding for a case that gold stud bump and
electroless nickel/copper/gold bump are applied.
BEST MODE FOR CARRYING OUT THE INVENTION
Explanation on an example of the present invention referring to the
attached drawings follows.
[Bump Formation of IC Chip for a Test]
FIG. 1A through FIG. 1C are sketches to describe the method of
formation of gold stud bump 140 before coining and FIG. 1D is a
sketch to describe the method of formation of gold stud bump 140a
that the end of which becomes even by coining process.
Referring to FIG. 1A through 1D, aluminum pad 120 is deposited to
IC chip 110 with the thickness of 1 .mu.m first. Then, after
protection film 130 comprised of SiN or polyamide is formed on an
aluminum pad 120 in 0.5.about.1 .mu.m thickness, I/O pad is formed
following from the formation of pitch with 100 .mu.m diameter that
reveals aluminum pad 120 by etching the protection film 130.
Then, gold stud bump 140 is formed using wire bonder above the I/O
pad. Since the end of gold stud bump 140 has a bit sharp shape,
gold stud bump 140a, the end of it is evened by performing the
coining process that applies the constant pressure to the end of
gold stud bump 140.
The coining process is performed to ease the alignment and contact
of the IC chip 110 with the board as well as to reduce the contact
resistance by widening the contact area. Another reason to perform
the coining process is to prevent the damage of IC chip from an
over contact pressure to a specific I/O pad in contact with the
board if the height of the bump is uneven.
The same process is conducted in case that a copper stud bump is
used instead of a gold bump. FIG. 1E is a picture that shows the
gold stud bump 140 of FIG. 1C before coining and FIG. 1F is a
picture that shows the gold stud bump 140a of FIG. 1D after
coining.
FIG. 2A through FIG. 2D are cross-sectional views to describe the
method of formation of electroless nickel/copper/gold bump.
Referring to FIG. 2A through 2D, I/O pad is formed as in FIG. 1A,
except that a zinc layer 125 is formed by zincate treatment after
aluminum pad 120 is formed to activate aluminum for metal coating.
That is, after aluminum pad is formed in 2 .mu.m thickness by
sputtering method, either SiN protection film is deposited in 0.5
.mu.m thickness by thermal evaporation or polyimid organic
protection film in 1 .mu.m thickness by spin coating method, and
I/O pad is formed applying lithography process.
Next, nickel layer 142 of 10.about.15 .mu.m thickness is formed
after dipping the result material in a electroless nickel coating
solution of 90.degree. C. for 20.about.30 minutes. After
electroless copper coating solution 144 that is less hard than
nickel coating one is formed in 10 .mu.m thickness, a gold layer
146 of 0.1 .mu.m thickness is formed by gold coating for 30 minutes
using electroless gold coating solution around 60.degree. C.
Therefore, electroless nickel/copper/gold bump 145 is approximately
25 .mu.m in thickness as a whole.
The use of gold layer 146 is to protect the nickel layer 142 and
copper layer 144 from oxidation and to increase the electric
conductivity as well. The copper layer 144 with good ductility that
lies between nickel layer 142 and gold layer, is making the plastic
deformation easier when IC chip 110 is thermo-compressed to the
board and widens the electric contact area as a result. FIG. 2E is
a picture to show electroless nickel/copper/gold bump of FIG.
2D.
[Making Board for a Test]
A FR-4 organic board in 1 mm thickness is made for a test board.
The surface of the board is formed with a metal electrode
comprising of multiple layer of Ni/Cu/Au, and the part outside the
electrode is protected by solder mask.
[Making NCA]
NAC in the form of a film or a paste is made mixing epoxy resin,
hardener, and non-conductive particles.
NCA film is produced as follows. 10 g of solid-phase bisphenol A
type epoxy resin, 25 g of liquid-phase bisphenol F type epoxy
resin, 20 g of solid-phase phenoxy resin, 46.6 g of solvent mixture
of methylethylketone and toluene with the ratio of 1:3 in vol %
(corresponding to 10.8 g of methylethylketone and 35.8 g of
toluene), 15 g of liquid-phase imidazole type hardener, and
non-conductive particles comprising of SiO2 and SiC with the size
of 0.1.about.1 .mu.m and with smaller thermal expansion coefficient
and dielectric constant are mixed together.
The component materials of the NCA film are listed above in
specific weight amounts. The NCA film is effective when the
component materials are used in the following ranges of percentage
weight of the film. The solid phase bisphenol A type epoxy resin
can be 6-10 wt %. The liquid-phase bisphenol F type epoxy resin can
be 15-25 wt %. The solid-phase phonxy resin can be 12-18 wt %. The
solvent mixture with methylethylketone and toluene with ration of
1:3 in vol % can be 32-40 wt %. The liquid-phase imidazole hardener
can be 8-14 wt %. And the non-conductive SiO2 or SiC particles can
be 6-20 wt %.
A Mechanical mixer is used for mixing and solid-phase bisphenol A
type epoxy resin, liquid-phase bisphenol F type epoxy resin,
solid-phase phenoxy resin, solvent mixture of methylethylketone and
toluene are mixed for 3 hours at a constant temperature of
80.degree. C. to obtain a homogeneous mixture. Then, using the same
mechanical mixer, non-conductive particles and hardener are mixed.
Then a film with constant thickness of 10.about.50 .mu.m is made on
a release paper film using doctor blade method.
Here, the film is left for one hour at 80.degree. C. to remove the
solvent and is mixed in a way that the hardener is 15.about.30 wt %
of the epoxy resin and the non-conductive particle is 10.about.30
wt % of the whole NCA film. The non-conductive particle is added in
order to lower the thermal expansion coefficient of NCA film.
The thickness of NCA film is decided upon the thickness of the bump
formed, however, is made to be 10.about.50 .mu.m so that bump with
various sizes can be employed. It is desirable to add an epoxy
resin adhesion enhanced layer with the thickness of 2.about.5 .mu.m
to both sides of NCA film so that the adhesive strength of the film
is increased. In a case that large amounts of inorganic powder is
contained in NCA film to lower thermal expansion coefficient, an
adhesion layer between semiconductor chip and board may not
function properly because the area of resin that has adhesive
strength among the adhesion area of NCA film becomes smaller.
Therefore, an adhesion enhanced layer in formed by lamination at
both sides of the NCA film that has smaller thermal expansion
coefficient. This adhesion enhanced layer also experiences
hardening by heat during the thermo-compression process, making
adhesion better by contacting the whole of semiconductor chip and
organic board, therefore significantly enhancing the adhesive
strength comparing with that of NCA film that contains
non-conductive particle of single-layer (one side) structure, and
has no effect on conductivity between bump of the chip and
electrode of the board. Here, adhesion enhanced layer is comprised
of the same elements with those of resin part except for
non-conductive particle of the NCA film, and the thickness is just
decreased to 2.about.5 .mu.m.
Meanwhile, NCA paste is a lot simpler in its composition than those
of NCA film. That is, 30.about.50 g of liquid-phase imidazole type
hardener is mixed with 100 g of liquid-phase bisphenol A or F type
epoxy resin and non-conductive particles SiO2 or SiC with the size
of 0.1.about.1 .mu.m is mixed 10.about.30 wt % to this NCA paste
resin that is composed as above. Mixing process is to mix them
until it becomes homogeneosus using mechanical mixer room
temperature.
The components of the NCA paste are listed above in specifc weight
amounts. The NCA paste is effective when the component materials
are used in the following ranges of percentage weight of the film.
The liquid-phase bisphenol A or F type epoxy resin can be 40-75 wt
%. The liquid-phase imidazole type hardener can be 15-30 wt %. And
the non-conductive SiO2 or SiC particles can be 10-30 wt %.
[Method for Flip Chip Bonding]
Explanation on a method for flip chip bonding referring to FIG. 3
follows. First,in the case of NCA paste, IC chip 110 that a bump
147 is formed is aligned to metal electrode 220 after fixed amount
of NCA paste 230 is coated to the board 210 using injection
equipment or screen printer equipment. Here, bump 147 can be gold
stud bump (140 of FIG. 1C) that has sharp end, or gold stud bump
(140a of FIG. 1D) that has flat end, or non-electrolyte
nickel/copper/gold bump (145 of FIG. 2D).
Since NCA paste 230 becomes hardened within 5 minutes, if IC chip
110 and board 210 is thermo-compressed under the pressure of
3.about.5 kgf/cm2 at 150.degree. C., bump 147 is plastically
deformed and is contacted with metal electrode 220, therefore, the
bump 147 and the metal electrode 220 is stably connected
mechanically and electrically as a result.
In the case of NCA film, after the side of NCA film is
thermo-compressed to the board 210 under the pressure of 1.about.2
kgf/cm2 at 80.degree. C., release paper film is removed, and
electrode 220 of the board 210 and non-solder bump 147 of the chip
110 is connected using NCA film by the align process.
FIG. 4A and FIG. 4B are cross-sectional views to present the case
of flip chip bonding by gold stud bump and electroless
nickel/copper/gold bump, respectively.
INDUSTRIAL APPLICABILITY
NCA in the present invention has smaller coefficient of thermal
expansion and dielectric constant and exhibits superior mechanical
and electrical features as well as high reliability compared to
conventional NCA. Also it is less expensive than ACA since, unlike
ACA, it does not contain high-priced conductive particles. Also it
can be made in the form of a film and a paste, therefore, can be
used appropriately as needed.
Since the flip chip bonding method in this invention uses
non-solder bump it is environmentally friendly. This method is also
highly competitive in cost and productivity since it can employ
existing flip chip process and equipment that use polymer
conductive adhesives. Also, contact resistance between IC chip and
board is low since contact area is wide due to the bump designed to
make high plastic deformation possible toward electrode that is
formed on board.
Also, it is clear that the scope of the claim is not limited only
to the compositions stated in the examples in the present invention
and equally contains the combination of similar compositions.
Embodiments of the present invention are not limited only to the
above, and it is evident that it can be diversely modified by a
person who has ordinary knowledge in the appropriate field, within
the technical idea of the present.
* * * * *